Other owners of mineral rights, Reeves

Long story, but after 3 years our family has managed to get division orders on my mothers estate. We have rights to PSL Block C-6 Section 16 and Section 17, referred to as Gulf Bertha-Hoefs Lease. Even after dealing with all the intricacies of getting the paperwork in place to obtain my mothers rights I am just beginning to realize the octopus of all the different tenacles of the entities (government/private companies) and find new things on a daily basis.

I know that my grandmother’s 11 brothers and sisters probably left rights to their children.

My question, how can I find out other owners of the rights to these Sections?

Thanks in advance for any help.